Significance of antepartum cardiotocography in normal pregnancy

Abstract

Antepartum cardiotocographs (CTGs) were obtained at weekly intervals from 34 weeks onwards and twice weekly from 40 weeks onwards in 91 strictly normal pregnancies. The Fischer score was used to assess the 594 CTGs obtained. Ominous patterns were not encountered but 7.2 per cent of CTGs showed a suspicious pattern. Absence of accelerations and an oscillatory amplitude of less than 10 beats/minute contributed to respectively 95 and 88 per cent of these patterns. The combination of reduced variability and absence of accelerations accounted for 84 per cent of suspicious CTGs. This pattern is compatible with normal pregnancy even when fetal movements are present. One-third (37 per cent) of perfectly normal pregnancies had a suspicious CTG on at least one occasion and in 9 per cent of cases it was found twice or more. This should be borne in mind when using antepartum CTG in the surveillance of high-risk pregnancy.